What is the effect of the Court of Appeal's failure to give a jury a cautionary instruction on witness credibility?

We find the case of People v. Dickey (2005) 35 Cal.4th 884 instructive. In that case, two witnesses claimed that Dickey had made admissions concerning his involvement in a murder. Dickey testified that he did not make the statements attributed to him. (Id. at pp. 896-899.) In concluding that the failure to give CALJIC No. 2.70 was harmless error, the Dickey court observed, "the court, while neglecting to give the cautionary instruction, did in other respects thoroughly instruct the jury on judging the credibility of witnesses. The jury was instructed on the significance of prior consistent or inconsistent statements of witnesses, discrepancies in a witness's testimony or between his or her testimony and that of others, witnesses who were willfully false in one material part of their testimony being distrusted in other parts, weighing conflicting testimony, evidence of the character of a witness for honesty and truthfulness to be considered in determining the witness's believability, and was given a general instruction on witness credibility that listed other factors to consider, including a witness's bias, interest or other motive, ability to remember the matter in question, and admissions of untruthfulness." (Id. at p. 906.) The court noted that "given these instructions, and given the extensive impeachment of [the witnesses who testified to the alleged admissions] raising credibility issues to which the instructions were pertinent [fn. omitted], the jury was unquestionably aware their testimony should be viewed with caution." (Id. at pp. 906-907.)